Magnetic hysteresis is a property all ferromagnetic materials, whereby the materials magnetization is dependent on its magnetic history. Stoner-Wohlfarth theory describes the hysteresis loops of an ideal single domain (SD) grain and an assemblage of randomly oriented SD grains.
Physical Principles
When a magnetic field (B) is applied to an initially demagnetized ferromagnet, it will become magnetized following an initial magnetization curve (segment ‘a’ in the figure below). As B is increased M linearly increases (segment ‘a’). If B is reduced to zero within this linear low-field segment, the magnetization is reversible and also reduces to zero. As B is increased beyond the linear segment, the slope of the curve increases. If B is now reduced to zero, M does not reduce to zero but istead follows path ‘b’ in the figure and retains a magnetic remanence, Mr (which is an IRM). If further increases in B result in no further increases in M, the magnetization becomes saturated, and is referred to as the saturation magnetization, Ms. As B is reduced to zero, the magnetization falls to Mrs, which is the saturation remanence (saturation IRM). Applying the field in the opposite direction reduces the IRM until the magnetization is reduced to zero, in a field Bc, which is called the coercivity. Increasing B in the negative direction results in saturation in the opposite direction. Cycling of the field causes the magnetization to follow a hysteresis loop as shown in the figure. If the field is cycled without reaching saturation, the magnetization follows a minor hysteresis loop. The coercivity of remanence, Bcr, is the field (when applied antiparallel to Mrs) required to reduce Mrs to zero.
^ Day, R., Fuller, M. D., & Schmidt, V. A. (1977). Hysteresis properties of titanomagnetites: grain size and composition dependence. Phys. Earth Planet. Inter., 13, 260–266, doi: 10.1016/0031-9201(77)90108-X.
^ Roberts, A. P., Y. L. Cui, and K. L. Verosub (1995), Wasp-waisted hysteresis loops: Mineral magnetic characteristics and discrimination of components in mixed magnetic systems, J. Geophys. Res., 100, 17,909–17,924, doi: 10.1029/95JB00672.
^ Tauxe, L., T. A. T. Mullender, and T. Pick (1996), Potbellies, wasp-waists, and superparamagnetism in magnetic hysteresis, J. Geophys. Res., 101, 571–583, doi: 10.1029/95JB03041.
^ Fabian, K. (2003), Some additional parameters to estimate domain state from isothermal magnetization measurements, Earth Planet. Sci. Lett., 213, 337–345, doi: 10.1016/S0012-821X(03)00329-7.
Magnetic Hysteresis
Table of Contents
Physical Principles
When a magnetic field (B) is applied to an initially demagnetized ferromagnet, it will become magnetized following an initial magnetization curve (segment ‘a’ in the figure below). As B is increased M linearly increases (segment ‘a’). If B is reduced to zero within this linear low-field segment, the magnetization is reversible and also reduces to zero. As B is increased beyond the linear segment, the slope of the curve increases. If B is now reduced to zero, M does not reduce to zero but istead follows path ‘b’ in the figure and retains a magnetic remanence, Mr (which is an IRM). If further increases in B result in no further increases in M, the magnetization becomes saturated, and is referred to as the saturation magnetization, Ms. As B is reduced to zero, the magnetization falls to Mrs, which is the saturation remanence (saturation IRM). Applying the field in the opposite direction reduces the IRM until the magnetization is reduced to zero, in a field Bc, which is called the coercivity. Increasing B in the negative direction results in saturation in the opposite direction. Cycling of the field causes the magnetization to follow a hysteresis loop as shown in the figure. If the field is cycled without reaching saturation, the magnetization follows a minor hysteresis loop. The coercivity of remanence, Bcr, is the field (when applied antiparallel to Mrs) required to reduce Mrs to zero.Hysteresis Measurements
Variable Field Translation Balance (VFTB)
Vibrating Sample Magnetometer (VSM)
Data Analysis
Hysteresis Parameters
Day Plot
One of the most common methods of analyzing hysteresis data is the Day Plot[1]Hysteresis Shape
Pot-bellied and wasp waisted[2] [3]Shape parameter[4]
Typical Features of Common Minerals
Single DomainPseudosingle Domain
Multidomain
References
Further Reading
Can be removed if not needed.
See Also
Stoner-Wohlfarth TheoryDay Plot
Isothermal Remanent Magnetization (IRM)
First-order Reversal Curve (FORC) Diagrams
Transient Hysteresis
Minerals:
Hematite
Magnetite